Quantitative parameters of intravoxel incoherent motion diffusion weighted imaging (IVIM-DWI): potential application in predicting pathological grades of pancreatic ductal adenocarcinoma.

Background: The aim of this study was to compare intravoxel incoherent motion diffusion weighted imaging (IVIM-DWI) parameters such as standard apparent diffusion coefficient (ADC(standard)), pure diffusion coefficient (D-slow), pseudodiffusion coefficient (D-fast) and perfusion fraction (f) for differentiating pancreatic ductal adenocarcinoma (PDAC) with different pathological grades. Methods: Institutional Review Board of our hospital approved this study protocol. Subjects comprised 38 PDACs confirmed by pathology. Pancreatic multiple b values DWI with 15 b values of 0, 10, 20, 40, 60, 80, 100, 150, 200, 400, 800, 1,000, 1200, 1,500, and 2,000 s/mm(2) was performed using GE Discovery MR750 3.0T scanner. ADC(standard), D-slow, D-fast and f values of all PDACs were calculated using mono-and biexponential models. Parameters of well/moderately differentiated and poorly differentiated PDAC were compared using Independent Sample t-test. P values < 0.05 were considered significant. Results: Mean Dslow value of well/moderately differentiated PDAC was significantly lower than that of poorly differentiated PDAC (0.540x10(-3) vs. 0.676x10(-3) mm(2)/s, P< 0.001). Mean f value of well/moderately differentiated PDAC was significantly higher than that of poorly differentiated PDAC (60.3% vs. 38.4%, P< 0.001). The area under curve value of f in differentiating well/ moderately differentiated PDAC from poorly differentiated PDAC was slightly higher than that of D-slow (0.894> 0.865). When the D-slow value was less than or equal to 0.599x10-(3) mm(2)/s, the sensitivity and specificity were 100% and 84.6% respectively. When f value was greater than 49.6%, the sensitivity and specificity were 92.0% and 84.6% respectively. Conclusions: Dslow and f derived from IVIM-DWI model can be used to distinguish well/ moderately differentiated PDAC from poorly differentiated PDAC. And to serve this purpose, Dslow and f have high diagnostic performance. IVIM-DWI is a promising and non-invasive tool for predicting pathological grade of PDAC.